Airless spray pumps for the spraying of paints and other coatings.
Airless spray pumps for the spraying of paints and other coatings via the airless method are well known and have traditionally been divided into two types, diaphragm pumps for the lower end of the market and reciprocating piston pumps for the higher end.
An airless spray pump is provided with a single-acting piston pump which allows the use of a low-cost yoke drive. Motor and pump shaft are offset for most efficient force utilization. The main drive housing has a motor mounted to the rear thereof A gear assembly uses gear teeth which are formed with a 5xc2x0 helical angle and have a 25xc2x0 pressure angle. This geometry combines the higher efficiency of straight cut gears with the noise reduction typified in a helical design.
An eccentric is molded onto the front of the gear assembly and has located thereabout a bearing assembly which rides inside a yoke. The yoke moves vertically on guide rods which are retained in pockets of the drive housing. The yoke is molded of plastic as is the gear assembly leading to lower cost and easier manufacture.
The pump rod is provided with a cap over the top end thereof which has bearing. Pump assembly is designed as a single acting pump, that is, the pump only pumps on the downward stroke and loads on the upward stroke. This allows the components of the drive train, including the yoke and gear, to be much lighter as the yoke ends up being more of a guidance device rather than a force-applying device.
The motor and pinion are offset from the centerline of the pump assembly. This arrangement does not have any significant cantilevering as the pump rod, pinion, yoke, eccentric and cap are all located in the same plane. The location of the rod and the single acting pump with respect to the gear centerline reduces the thrust loads on the yoke. The location of the pinion on the gear partially offsets and reduces the pump forces on the gear shaft and bearings. By locating the eccentric bearing directly on the end of the pump rod cap which is press-fit it eliminates the transfer of pumping force through an intermediate member such as the yoke which provides longer life, efficiency and allows the manufacture of a more inexpensive yoke assembly.
The shaft packing assembly is comprised of a packing housing which screws into the pump housing and which contains a felt member which has been soaked with throat seal lubricant or other solvent or lubricant. A stack of v-packings are compressed in place by wave spring which is tightened by tightening the seal housing into the pump housing.
The inlet check is provided with a check ball and a check seat which is pressed into a check housing and which is held in place by a retainer. These parts all press-fit into one another such that the complete assembly be merely screwed into main pump housing for replacement. Similarly, outlet check assembly is formed of an outlet check housing which is screwed into a pump housing and similarly is provided with a check ball held in place by a retainer. The outlet passageway is angled relative to the axis of the pump shaft. This allows the outlet check assembly to operate essentially via gravity and yet requires only the drilling and provision of one passageway while maintaining an essentially vertical ball-seat relationship.
These and other objects and advantages of the invention will appear more fully from the following description made in conjunction with the accompanying drawings wherein like reference characters refer to the same or similar parts throughout the several views.